Acta Phys. -Chim. Sin. ›› 2010, Vol. 26 ›› Issue (04): 921-926.doi: 10.3866/PKU.WHXB20100446

• CATALYSIS AND SURFACE STRUCTURE • Previous Articles     Next Articles

Surface Modification of Mg-Al Hydrotalcite Mixed Oxides with Potassium

ZHANG Ye-Xin, SU Qing-Yun, WANG Zhong-Peng, GAO Xi-Yan, ZHANG Zhao-Liang   

  1. Institute of Internal Combustion Engine, Dalian University of Technology, Dalian 116024, Liaoning Province, P. R. China; College of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022, P. R. China
  • Received:2009-11-19 Revised:2010-02-26 Published:2010-04-02
  • Contact: ZHANG Zhao-Liang E-mail:chm_zhangzl@ujn.edu.cn

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Abstract:

The surface modification of Mg-Al hydrotalcite mixed oxides (MgAlO) with K was investigated using X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), in situ infrared (in situ IR) spectroscopy, and temperature-programmed desorption of CO2 (CO2-TPD).We found thatKwas highly dispersed on the surface of MgAlO when the loading amount was less than 8% (w). New Lewis base sites were formed through the interaction between K and MgAlO. The weakly basic Mg(Al)-O-K resulted from the proton substitution of Mg(Al)-OH with K. Mg-O-K was obtained by combination with strongly basic O2- sites. At a K loading between 5% (w) and 8% (w), the quasi free KOx species that interacted weakly with the support and showed stronger basicity than Mg-O-K was formed. The increase in basicity of K/MgAlO can be attributed to charge transfer from K to the surface oxygen anions, which increases the negative charge of the strongly basic sites.

Key words: In situ IR, Hydrotalcite, Potassium, Surface modification, Basic site